Unlocked Iphone 8 plus invalid issue

[st3phi3babii]

I have a fully unlocked iPhone 8 plus from tmobile and sprint keeps telling me that the imei number is invalid. But that's impossible because I can pull it up anywhere and it's valid and fully unlocked and idk what to do so I can activate my sim on it. It's not blacklisted or anything and I see too many people having this issue with sprint. So it has to be an issue on your end and I need a solution asap.

[mamatle50]

Please let me know if you get a response I am having same issue and Tmobile/Sprint pretty much refuses to accept that the phone is not actually unlocked despite apple telling them it was.